The long-range goal of this project is the quantitative determination of the solvation and ion-pair complex formation properties of the trivalent lanthanide metal-ions. The experimental technique will involve the direct observation of the cation and its primary solvation shell by hydrogen-1, carbon-13, and metal-ion nuclear magnetic resonance (NMR) spectroscopy using a multinuclear, superconducting, Fourier transform 400 MHz spectrometer. This observation will permit the determination of accurate values of the number of water molecules bound to the ion, the extent of competitive solvation in aqueous solvent mixtures, the extent of inner-shell ion-pairing and the composition of the species produced in solutions of different anions, and the local electronic and molecular environment of the ion itself. The measurements will be made in the liquid and solid state to provide an evaluation of the maximum ion coordination numbers, the factors which affect these values, variations of coordination number in the series, and the structure of the species present. This information is needed for the lanthanides for a variety of reasons. These ions are used in numerous industrial processes, as chemical shift reagents in NMR studies of biochemical systems, and increasingly, as probes in studies of macromolecular structures and reaction mechanisms.